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Commercial allergen extract preparations of whole cereal grains were examined in vitro for their reactivity with the human haemolytic complement cascade. Total haemolytic complement was consumed in a dose-dependent manner which did not correlate with the protein nitrogen content or bacterial endotoxin contamination of the extracts. Alternative pathway activation was shown by C3 conversion in the presence of EGTA while classical complement components C1, C4 and C2 were also much decreased in serum which was free of detectable specific antibody. Very small amounts of allergen extract initiated the formation of complement-dependent factors which were chemotactic for human polymorphonuclear leucocytes. These data suggest a potential for complement activation in vivo by ingestion, inhalation, or injection of cereal grain products.

Ground whole rye and airborne rye dust of comparable size distribution were tested for their ability to activate the complement cascade via the alternative pathway. Precipitin-negative pooled normal human serum was incubated with increasing amounts of the two rye dusts. Electrophoresis of the resultant supernatant fluids demonstrated the conversion of the proactivator of the third component of complement to the gamma-migrating activator of the third component. This activation was completely prevented by pre-treating the serum with the chelator EDTA, while pre-treatment with EGTA allowed suboptimal arc conversion, strongly implying that complement was activated via the alternative pathway. Quantification of the supernanant fluids showed dose-dependent complement consumption as defined by both CH100 immunodiffusion and CH50 tube haemolytic techniques. Airborne rye dust showed a greater quantitative potential than ground whole rye for activating the alternative pathway. These results indicate the possibility of the direct action of airborne organic dusts on the induction of inflammatory sequelae in the lungs of both sensitized and unsensitized individuals.